It seems like you're over-complicating things. If you're going to need to call the code within an event handler from different places, it's a good idea to abstract that out to a different method. You can attach the same event handler to the PictureBoxes which then call that method.
for(int i = 0; i < PictureBoxArray.GetLength(0); i++)
{
for(int j = 0; j < PictureBoxArray.GetLength(1); j++)
{
//attach handler
PictureBoxArray[i,j].Click += pictureBox_Click;
}
}
void pictureBox_Click(object sender, EventArgs e)
{
MyMethod();
}
void parentForm_Click(object sender, EventArgs e)
{
MyMethod();
}
private void MyMethod()
{
//method to be called
}